Snap action assembly



Jan. 30, 1968 w, fwATso 3,366,756

SNAP ACTION ASSEMBLY Filed April 4, 1966 v I 2 Sheets-Sheet 1 INVENTOR. WAYNE T. WATSON Jan 30, 168 w. T. WATSON 3,366,756

SNAP ACTION ASSEMBLY Filed April 4-, 1966 2 Sheets-Sheet WAYNE T. WATSON Mam;

3,366,756 Patented Jan. 30, 1968 3,366,756 SNAP ACTION ASSEMBLY Wayne T. Watson, Mansfield, Ohio, assignor to Norwalk Thermostat Company, Norwalk, Ohio, a corporation of Ohio Filed Apr. 4, 1966, Ser. No. 539,996 Claims. (Cl. 200-67) This invention relates to snap action assemblies and more particularly to such assemblies suitable for miniaturization and affording a wide range of operating characteristics.

An object of this invention is to improve snap action assemblies. Another object is to reduce the size of the snap action assemblies particularly those affording various adjustments to alter in a controlled manner their operating characteristics. A third object is to increase the range of control of the operating characteristics of the snap action assemblies. A fourth object is to accurately establish the operating parameters of a snap action assembly suitable for mass production. A fifth object is to produce an abrupt transition of forces in a snap action assembly particularly as applied in electrical switches wherein contact erosion is avoided by the transition from a relatively high pressure to an open contact condition without an intermediate operating state in which the contact pressure is low or the engagement intermittent. Another object is to afford an adjustment of the ratio of mechanical differential movement to contact gap in a snap action switch assembly. A further object is to improve thermally actuated snap action switches.

In accordance with one embodiment of this invention, the snap action assembly comprises a relatively rigid frame in which is mounted a flexible blade extending along the longitudinal axis of the frame and partially through the open interior thereof. The longitudinal sides of the frame are placed in tension and the flexible blade in compression to a degree such that the tension forces and compressive forces are misaligned. The assembly is mounted from a portion of the flexible blade intermediate its ends. Its position is established at one end by a stop means such that the displacement generally normal to the frame at the other end tends to carry the line of tension as it extends along the plane of the rigid frame across the lines of compression extending between the mounting position of the flexible blade and its ends. As this transition occurs an overcenter snap action is experienced wherein the end of the frame against the stop transfers its position to a new state of equilibrium. A self return feature is afforded in this structure by use of a second stop which constrains the range of travel of the actuated end of the frame, coupled with a preform in the flexible blade in its region between the mounting position and the actuated end of the blade tending to cause the frame to shift the line of tension forces across the line of compressive forces in a return direction when the actuating force is removed from the actuated end of the frame. Alternatively, the travel limits for the assembly can be spaced so that it is shifted from one stable position to a second stable position and a resetting manipulation must be undertaken to return the assembly to its initial position.

A feature of this invention is the utilization of a rigid frame as one blade of the snap action assembly to afford a precise control of the operating parameters of the assembly. Another feature is the mechanical configuration of the elements of the assembly permitting the elements to be produced by high production stamping processes without a loss in a precision of the operating characteristics. In particular indexing surfaces are afforded which in conjunction with convenient adjusting means enable the snap action elements to be assembled in a self retaining assembly and to be adjusted to the operating parameters desired.

Another feature of the invention is the adaptability of the snap action structure to either open or enclose mounting.

A further feature is the compact nature of the snap action which enables it to be mounted with a housing having an outside dimension of an inch and a quarter in length and half an inch in width or to be mounted on a pile-up of blades on a mounting base which for convenience can be secured on a single rivet with intermediate insulators whereby electrical isolation of the several elements may be afforded in a convenient open mounting.

Another feature resides in the utilization of the snap action assembly in thermally actuated switches of various configurations.

A further feature resides in the utilization of the snap action assembly as an electrical switch element for various contact configurations including normally opened and normally closed contacts and single and double throw operations.

A sixth feature includes the adaptability of the snap action assembly to manual reset applications as by a reset element which transfers the assembly, arranged to have two stable positions spaced by an intermediate region of instability, across the region of instability.

The above and additional objects and features will be more fully understood from the following detailed description when read with reference to the accompanying drawings wherein:

FIG. 1 is a side elevation of one form of snap action assembly as applied to a single pole single throw switch;

FIG. 2 is a side elevation of another application of the snap action assembly as utilized in a double pole double throw switch;

FIG. 3 illustrates a miniature switch in side elevation with the enclosing casing sectioned to show the interior and including adjusting means for adjusting the compressive and tension forces for the contact blades;

FIG. 4 is a side elevation of another form of snap action assembly wherein adjustment is afforded for the positioning of the flexible blade at the actuating end of the assembly;

FIG. 5 is a perspective view of the snap action assembly of FIG. 3;

FIG. 6 is a side elevation of the snap action assembly in a thermally actuated switch pile up;

FIG. 7 is a side elevation of the snap action assembly mounted for bistable operation and including a thermal time delay tripping mechanism and a manual reset means; and

FIGS. 8 and 9 depict the relative position of the flexible and rigid "blade of the monostable snap action assembly in a stable state of equilibrium and the unstable state of equilibrium occurring at the snapover point respectively.

The basic snap action assembly of this invention as best illustrated in FIG. 5 comprises a stiff outer blade 21 cooperating with a flexible inner blade 22. The outer blade is generally made up of a relatively rigid stock material and formed with an open center portion 23 in which the inner blade is free to flex. The outer blade is stiffened longitudinally by flanges 24. Inner blade 22 is maintained under compression between points of coupling adjacent the longitudinal ends of the outer blade. In the example of FIG. 1 a flange 25 is turned toward the flexible blade adjacent one end of the outer blade 21. A slot is provided in the central portion of the end flange 25 essentially in the plane of the lower surface of the major face of blade 21 for the reception of a tongue 26 on the end of flexible blade 22. Blade 22 is provided with shoulders adjacent the tongue 26 which engage end flange 25 011 either end of the slot. The opposite end of the flexible blade is secured to the blade 21 in the electrical switch embodiment of FIG. 1 by abutting it against a flange 27 on the actuated end of the blade 21 and securing it thereto by passing the shank of a contact rivet 28 through suitable registering apertures in the blades 22 and 21, and by form ing over the end of the shank as at 29 to provide a unitary structure. In this manner the inner blade 22 is effectively a cantilever extending from the region between the flat underface of the contact rivet 28 and the flat face of outer blade 22 so that when the blade 22 is placed under compression by engaging its tongue 26 in the slot of flange 25 a moment is developed at the point of coupling of the two blades adjacent the actuated ends tending to cause the blades to shift to a position in which the compressive line of force developed along the fleXible blade 22 is superimposed upon the tension line of force developed along the blade 21.

The flexible blade is mounted upon a tab like protrusion 31 which in a switch construction may be formed out of a terminal structure 32 to provide a coined area of relatively limited extent longitudinally of the flexible spring upon which the blade is clamped as by rivet 33. Thus, the flexible blade is supported from its mounting base as a cantilever which through the tendency of the flexible blade to straighten and align itself from its mounting beneath contact 28 develops a moment tending to bring the compressive forces in the flexible blade into alignment with the tension forces developed in the rigid blade 21. A stop in the form of an adjustable screw 34 limits the over travel of the contact supporting end of the blades on one side of the position of unstable equilibrium where the bending moments of the cantilever mountings and the overcenter section of the tension compressive forces are balanced. An electrical contact 35 mounted on a terminal 36 permits the travel of the actuated end of the blades on the other side of the position of unstable equilibrium.

The snap action structure illustrated in FIG. 1 is actuated by the application of force generally normal to the major face of blade 21 in the region between the flange 25 and a plane normal to the blade 21 and passing through the mounting rivet 33. This force can be imposed by means of a plunger 37 mounted for reciprocation, for example as illustrated in FIG. 3.

In order to provide a self-restoring feature in this snap action assembly, flexible blade 22 is provided with a form intermediate its end as at flange 25 and its mounting region as at tab 31. The form 38 imposes a bias tending to displace the blade 21 from the terminal 32 and mounting region 31 and thus tending to oppose forces imposed by the actuating plunger 37. As the force on the actuating plunger 37 is relieved the resilence of blade 22 tends to move the end of the assembly upward and as that end moves upward the compressive forces forming from the ends of the resilient blade 22 to the mounting tab 31 come into alignment with the tension forces extending longitudinal of blade 21 to balance these forces and create a condition of unstable equilibrium. Further displacement of the end of the blades from the terminal 32 creates an over center condition which causes the rapid shifting of the opposite end of the assembly away from the teminal 36 thereby separating the contacts 28 and 35'.

The circuit of switch of FIG. 1 is between terminals 32 and 36 and in the unactuated condition is normally open. When the switch is closed, its circuit extends from terminal 32 through tab 31, rivet 33, flexible blade 22, contact 28, to contact 35 and terminal 36. It is apparent that other arrangements of contacts can be employed with the illustrated snap action assembly. If a normally closed switch is desired the terminal 36 and its contact 35 could be mounted to engage the upper face of blade 21 in the location contacted by adjustable stop 34. This normally closed contact could be mounted for adjustment as by a screw mounting to its terminal. An opposite travel limit could be positioned in the location of contact 35 in FIG. 1 for such an arrangement.

In FIG. 2 essentially the same snap action mechanism as shown in FIG. 1 is illustrated as applied to a multicontact switch. The flexible blade 22 is maintained under compression between the ends of stiff blade 21 and the assembly of the two blades is supported from mounting tab 31 on terminal 32. Contact 23 on the end remote from the actuating plunger is spaced from contact 35 on terminal 36 when no actuating force is imposed on the plunger. With no force on the plunger 37, the position of the end spaced from the plunger is established by a contact 41 mounted on a terminal 42 in the fashion of contact 35 in terminal 36. Contact 41 cooperates with a contact 43 on the upper face of blade 21 which may be integral with the contact 28. A third set of contacts comprising contact 44 on the upper face of blade 21 and adjacent the plunger engages contact 45 on terminal 46 when no actuating force is imposed on plunger 37. In this arrangement the actuating plunger 37 has been shown in engagement with blade 21 in the region between the contact 44 and the projection of the plane normal to blade 21 passing through the axis of mounting rivet 33. Thus the actuating means is positioned closer to the center of the rigid blade in this embodiment than in FIG. 1. Alternatively, one of contacts 45 or 41 can be mounted to move normal to blade 21 and actuate the snap action assembly in its over center operation.

With no actuating force imposed, the circuit is completed from the terminal 32 through the blade 22 and 21 to the contacts 44 and 43 and from those contacts to their respective contacts 45 and 41 coupled to terminals 46 and 42. Application of an actuating force through depression of the plunger 37 toward terminal 32 initially separates contacts 44 and 45. Further displacement of the plunger 37 toward terminal 32 carries the line of compression projected along the lower surface the major face of blade 21 across the line of compression between the mounting region 31 and the ends of blade 22 whereby the snap action occurs through the over center movement of the actuated end of the assembly to separate contact 43 from contact 41 and close contact 28 on contact 35. As in the embodiment of FIG. 1, the constraining of the snap action assembly at both limits of travel to less than the total travel available insures that some of the spring energy stored in blade 22 applies contact pressure between each set of contacts at the respective limits of travel.

Each of the structures shown in FIGS. 1 and 2 provided with suitable mountings (not shown). One typical form of mounting for the elements which also provides a housing for a miniature switch utilizing the snap action assembly of "this invention is shown in FIG. 3. This housing which can be molded of a suitable insulating material to dimensions of about an inch and one quarter in length by W inch in width and inch of height. It affords the support for the various elements primarily through the gripping of terminals 32 and 36 in suitable sockets formed between the housing body 47 and its cover 48.

A perspective of the snap action and contact assembly of the device of FIG. 3 is shown in FIG. 5. The terminal 32 has a tongue 49 which projects into a cavity in the end wall 51 of the body of the housing to index the position of terminal 32 and thus the snap action assembly transversely within the housing. Similarly an indentation 52 on the opposite side of the terminal 32 is engaged by a rib 53 on the inner face of housing cover 48 to afford a further indexing of the terminal 32. The rib 53 engages a similar indentation 54 in the terminal 36. A tongue 55 which mates with a cavity in the end wall 56 of housing 47 indexes the position of terminal 35 in that housing. Actuating plunger 37 which may be molded of a suitable insulating material is also sustained by the housing 47 in a suitable aperture molded therein while adjusting screw 34 is fitted within the tapped aperture 57 at the opposite end of the housing.

The snap action assembly of the unit of FIGS. 3 and includes the flexible blade 22 and the rigid blade 21, further stiffened by longitudinal flanges 24. The contact carrying end of blade 22 is longitudinally indexed with respect to blade 21 during the assembly of these elements by its abutment against end flange 27 formed on blade 21. It will be noted from FIG. 5 that the end flange 27 projects only partially across blade 21 in order to permit the circumference of contact 28 to extend between the two portions of the flange 2'7. The actuating end of blade 22 is secured to blade 21 by means of adjuster slide 58 which supplants the integral flange 25 of FIGS. 1 and 2. Slide 58 fits between flanges 24 and is guided thereby longitudinally of blade 21. It has a major reach parallel to and in face to face relationship with the surface of blade 21 remote from blade 22. A first oflset tab 59 integral with slide 58 extends away from blade 21 and is provided with a tapped aperture for the reception of an adjusting screw 61. The underside of of the head of the adjusting screw 61 is in abutting relationship with a tongue 62 formed out of the body of blade 21 adjacent its open center portion 23. Rotation of the screw causes reciprocation of the adjuster slide 58 longitudinally of the blade 21. The end of the adjuster slide adjacent the actuating end of blade 21 is provided with a tab 63 turned toward blade 21 and extending across its thickness and beyond its lower surface. Tab 63 is provided with a T-shaped slot 64 through which a tongue 65 integral with blade 21 and narrower than the width of blade 21 projects to be engaged by the p rimeter of the arms of the T slot. The depending body of the T slot receives a tongue 66 of flexible blade 22.

Adjustment of screw 61 to adjust the longitudinal position of adjuster slide 58 the compression imposed by the shoulders at the end of blade 22 and adjacent the tongue 66 engaging the tab 63 adjacent slot 64 places blade 22 in compression and blade 21 in tension. The actuating force required to be imposed on actuating plunger 37 to transfer contact 28 to engagement with contact 35 is adjusted by adjustment of the compression of blade 22. In actual manufacture the range of adjustment necessary to produce snap action assembly operating with parameters within rather narrow limits is rather limited. However, it is to be appreciated that the range of adjustment by the means illustrated can be quite extensive. Useful adjustment spans a range from an initial buckling of the region of blade 22 between support 33 and contact 28 to a range Where the blade sections on each side of support 33 approach semi-circles. At compressions in which blade 22 approaches a semi-circle the travel of the assembly is also affected materially by the degree of adjustment. However, for practical purposes it can be assumed that as compression developed by the adjusting means increases the actuating force is increased through the practical operating range of the structures illustrated.

The degree of adjustment of screw 34 in establishing the proximity of contact 28 to contact 35 adjusts the force and displacement required to be imposed on plunger 37 to cause the over center snap action of the assembly. The stop 34 is adjusted toward the contact 35 thereby reducing the gap between contacts 28 and 35 and carrying the assembly closer to its center position. As the center position is approached and the compressive and tension forces approach alignment, the force required to be imposed by the plunger 37 to cause operation of the switch is reduced and the travel of the plunger 37 to cause operation is reduced. This can be appreciated from a consideration of the diagrammatical representation of the switch in FIGS. 8 and 9.

As shown in the diagram of FIG. 8, when no actuating force is applied the line of tension AB corresponds to the underface of blade 21. In this condition the actuating plunger 37 and adjusting screw 34 position the major face of blade 21 essential-1y parallel to the mounting face for the intermediate portion of blade 22. As the plunger 37 is depressed the point A is rotated about the point B as a center until the line AB approaches an intersection with the points CD. The lines of compression in the blade 22 is represented by a line AC and a line DB. The superposition of these compression and tension lines as influenced by the moment created by the cantilever mounting of the ends of the section DB of flexible blade 22 causes the snap over of the point B to a position shown as B in FIG. 9 wherein the points C and D have been transferred to the opposite side of the line AB' from that shown in FIG. 8. At this time the form in the section of flexible blade 22 between A and C tends to bias the point A upward to its A position. As the force on actuator 37 is relieved and it is permitted to be displaced upward, the line A'B' tends to be rotated around the point B until it crosses the points OD. When it is slightly above these points to over-come the cantilever moments, the point B snaps upward to restore the elements to the position shown in FIG. 8. Thus by adjustment of screw 34 to adjust the position of point B the degree of displacement necessary to achieve snap action is adjusted in the assembly.

FIG. 4 shows another embodiment of this invention with an additional adjustment provided by adjusting screw 70 which passes through a suitable tapped hole in the terminal 32 to bear against the form region 38 providing the return bias for the snap action assembly. This assembly in other respects can be considered to be the equivalent of that shown in FIG. 1. This adjustment is afforded to adjust the ratio of the mechanical differential movement to con-tact gap within certain limits. As the projection of adjusting screw 70 is extended toward blade 21 the flexure of blade 22 caused by actuating plunger 37 tends to be concentrated between support 31 and contact 28 due to the displacement of form 38 upward. Hence, the ratio will be increased and thus a more abrupt transi tion will be experienced at the snap over position resulting in an increase in contact pressure when the contacts are closed and a more rapid transfer of the contact as the actuator 37 is carried across the transition region.

In FIG. 6 another application of the snap action assembly in a switch utilization is set forth. The snap action assembly is illustrated as a norm-ally closed switch utilizing a flexible blade 22, a rigid blade 21, an adjusting slide to adjust the tension compression forces 58, an actuator pin 72 corresponding to the pin 37, a mounting '73 for the flexible blade 22 corresponding to the tab 31 on terminal 32, a back stop in the form of engaged contacts 74 and 75 corresponding to the adjustable screw 34 engaging the headed region 29 and a front stop in the form of an adjustable screw 76 corresponding to the front stop cont-act 35. In this arrangement the switch is normally closed through a circuit from terminal 77, blade 78, mounting 73, blades 22 and 21, contact 74, contact 75, blade 79 and terminal 86. A bi-metal blade 81 constitute-s a thermally responsive element driving the actuating pin 72 which is adjustably mounted thereon by the screw base 82 of pin 72 threaded into a tapped hole in blade 81. The major assembly is supported in a stacked relationship on a rivet 83 from which the respective elements are insulated as by suitable insulating washers 84 having sleeves which fit along the shank of the rivet Within the apertures in the blades and terminals.

The structure of FIGURE 7 illustrates further refinement in a thermally actuated snap action switch where the snap action is bistable, and in addition sets forth a manual reset feature. The switch of FIG. 8 utilizes a bi metal actuator blade 81 the position of which is influenced by the heat developed in a heater 86 supplied over leads 87 and 88 coupled to terminals 89 and 90 in the stack. As blade 81 is heated by heater 86, its outer end flexes downward to displace an actuating pin 72 against the snap action assembly and cause the opening of normally closed contacts 74, 75. Thermal compensation is afforded by mounting the snap action assembly on bimetal blade and the contact 75 is mounted upon a resilient blade 79'which is formed to have a bias toward contact 74. In this arrangement no back stop is provided in the range of travel of the actuated snap action assembly wherein the self restoring bias of offset region 38 is effective. Thus, referring again to FIGS. 8 and 9, the point B after the over center snap action is effective is displaced to a position without limiting the over travel of that point such that it extends to the position B". In such a position it wil l be noted that with the relief of the displacing force imposed by pin 72, the end of blade 21 engaged by pin 72 can return to A" under the bias of form 38 as in FIG. 9. This return motion is insufficient to carry the tension line AB" across the compression lines A=C and DB and thus does not afford the over center snap action to return the assembly to its position illustrated in FIG. 8. In order to provide such a return action a manual reset in the form of pin 91 is provided.

The pin 91 carries a flange 92 which engages the bearing 29 to move the position B" in a manner such that the line BA" is carried across the compression lines A'C and B"C to enable restoration of the snap action assembly to its illustrated position. 'Pin 91 is mounted for reciprocation in sleeve 93 carried on rigid mounting bracket 94- extending from the stack of switch elements mounted on rivet 83. Normally pin 91 is biased by the pressure of blade 79 on its end to hold it in the illustrated position with the flange 92 bearing against the blade 85. Coupling through the pin 91 of blade 79 and blade 85 affords a further means of ambient temperature compensation inasmuch as the contact 75 tends to be displaced with the blade 85 as the ambient temperature changes.

The manual reset also affords an interlock which prevents inadvertent closure of contacts 74 and 75 when those contacts should remain open as indicated by the displacement of blade 81. During reset plunger 91 is pressed to move flange 92 into engagement with the bearing face 29 on the snap assembly. This moves contact 74 toward its reset position and also moves contact 75 out of range of the reset position of contact 74. As a result the contacts 74 and 75 cannot be closed while plunger 91 is depressed. As the plunger is released, blade 21 and contact 74 will be retained in their reset positions if actuator pin 72 has retreated tr-om its tripping position. If pin 72 has not retreated, blade 21 and contact 74 will follow the retracting flange 92 in the plunger and move out of their reset positions without engaging contact 75. Under these circumstances it is assumed that the over travel of the actuated end of the assembly will be insufficient to carry the point B" to a position wherein the line A"'B" crosses the lines AC and BD. Thus release of resetting force on pin 91 causes the pin to be returned to its illustrated position through the resilience of blade 79 when the flange 92 retreats from the bearing 29 the assembly again returns to its snap over position. wherein contact 74 is spaced from restored contact 75.

An alternate form of operation of the snap action assembly in an electrical switch construction is available wherein actuation of the blade occurs at the contact bearing end of the assembly. For example in FIGURE 7 contact 74 could be actuated through its cooperating contact 75 if blade 79 were the actuating element, as a thermally responsive bimetal blade, and the actuator of FIGURE 7, blade 81 were replaced by a stationary stop. This transposition of functions lends itself to both the monostable and bistable forms of operation as outlined in FIGURES 8 and 9.

It is evident from the above discussion that the invention lends itself to many combinations and variations. The front and back stop adjustment for the actuated end of the snap action assembly afford a means to adjust the over travel of the actuated end and thus affording a means to determine whether the assembly will be self restoring. The adjustment pin 70 adjusts the ratio of mechanical differential movement and contact gap. The adjusting slide 58 adjusts the compressive-tension forces in the assembly. The snap action assembly is applicable to a number of contact arrangements including normally closed and normally open contacts, single pole, single throw double pole, double throw and single pole double throw switch arrangements. The various mounting arrangements for the snap action assembly include enclosed mountings and open blade mountings for thermostat applications. Thus, this invention lends itself to incorporation of one or more of the above features. Accordingly, it is to be understood that the embodiments set forth are to be interpreted as illustrative only and are not to be read in a limiting sense.

Having described the invention, I claim:

1. A snap action switch comprising a relatively flexible resilient blade having a length substantially greater than its breadth, said blade being generally flat in its major plane and having a form adjacent one end to offset said one end from said major plane; a mounting region for said flexible blade intermediate said form and the end opposite said one end; a rigid blade forming a frame for an opening in its major plane, the opening having a width exceeding the Width of said flexible blade; means to secure the ends of said flexible blade to said rigid blade such that the portion of said flexible blade adjacent said form stands away from said rigid blade, said flexible blade being in longitudinal compression and said rigid blade being in tension, said flexible blade in a region intermediate its ends being free to move within the opening defined by said rigid blade in a direction normal to the major plane of said rigid blade; a first electrical contact rigidly secured to said rigid blade at its end remote from said form on said adjacent flexible blade; a support structure; a mounting means secured to said support structure and to said mounting region for said flexible blade to support said flexible blade, said rigid blade and said first contact for movement relative to said support structure; a second electrical contact arranged to cooperate with and be engaged by said first contact and supported by said support structure; and an actuating means engaged with said rigid blade and moveable generally normal to the major plane of said rigid blade adjacent its end adjacent said form on said flexible blade to carry the line of said tensile force between the ends of said rigid blade across the lines of compressive force between the ends of said flexible blade and said mounting region whereby the first contact is shifted in its angular relation to the second contact with a force of said actuating means and a force of said resilience of said flexible blade in the region of said form, said forces acting on the lever arm of said rigid blade.

2. A combination according to claim 1 including a screw mounted on said rigid blade for movement therewith independently of said support structure and having an axis parallel to the longitudinal axis of said rigid blade, a means coupling said screw to said means to secure said end of said flexible blade which is most proximate said form to said rigid blade and a threaded coupling engaged by said screw adjustably coupling said rigid blade and said means coupling said screw and said flexible blade.

3. A combination according to claim 1 including a mounting for said second electrical contact which is rigidly secured relative to said support structure.

4. A combination according to claim 1 wherein said support structure comprises a base, a first blade extending from said base and sustaining said mounting means, a first stop limiting the travel of the end of said rigid blade to which said first contact is secured in a direction away from said first blade, a second blade extending from said base to sustain said first stop, a second stop limiting the travel of the end of said rigid blade to which said first contact is secured in a direction toward said first blade, said second stop being sustained by said first blade, and a third blade extending from said base to sustain said actuating means.

5. A combination according to claim 1 including means on said rigid blade mounted for movement therewith independently of said support structure for adjusting the location longitudinally of said rigid blade of said means to secure one end of said flexible blade to said rigid blade.

6. A combination according to claim 1 including a first lug secured to and normal to the main face of said rigid blade, a bracket having a reach parallel to and abutting the major face of said rigid blade, a lug on said bracket adjacent and parallel to said first lug, said bracket being movable with respect to said rigid blade and carrying said means to secure one of said ends of said flexible blade to said rigid blade, and a screw-adjusted coupling between said first and second lugs and parallel to the length of said rigid blade.

7. A combination according to claim 1 wherein said actuating means is a thermally responsive means having a displacement which is a function of its temperature.

8. A combination according to claim 4 wherein said third blade is a thermally responsive bimetallic element which has an end remote from said base flexed toward and away from said rigid blade as a function of its temperature.

9. A combination according to claim 1 including means engaging said offset portion of said flexible blade on its face remote from said rigid blade, and means for displacing said engaging means toward and away from said rigid blade.

10. A snap action switch comprising a relatively flexible resilient blade having a length substantially greater than its breadth, an actuated end and an actuating end, said blade being generally flat in its major face and having a form adjacent its actuating end to form a relatively fiat offset of said major face; a mounting region for said flexible blade intermediate its longitudinal ends; a relatively stiff blade forming a frame for an opening in its major plane having a width exceeding the width of said flexible blade, said stiff blade having a transverse flange at its actuated end against which the actuated end of said flexible blade abuts; a contact secured to said blades at their actuated end; a tongue extending from said stiflt' blade at its actuating end; a first lug extending normal to the major face and length of said stiff blade adjacent its actuating end; a bracket having a reach parallel to and abutting the major face of said stiff blade; a second lug on said bracket adjacent and parallel to said first lug; a screw-adjusted coupling between said first and second lugs and parallel to the length of said stiff blade; a third lug on said bracket parallel to said second lug and extending from said reach in a direction opposite said second lug, said third lug having a slot embracing said tongue on said stiff blade; means to secure said actuating end of said flexible blade to said bracket; an electrical terminal; a mounting electrically and mechanically coupling said mounting region of said flexible blade and said terminal; a second terminal; a contact on said second terminal; support structure for supporting said first and second terminals in insulating relation to each other and positioned with said contacts engageable with each other; and actuating means engageable with said stifi blade at its actuating end and adapted to move said stiff blade generally normal to its major face to carry the line of tensile force between the actuated and actuating end of said stiff blade across the lines of compressive force between the ends of said flexible blade and said mounting region.

References Cited UNITED STATES PATENTS 2,669,618 2/ 1954 Bradley. 1,695,103 12/1928 Hook. 2,202,440 5/ 1940 Beach. 2,246,756 6/1941 Riche 200138.2 2,394,121 2/1946 Ulanet 200l38.2 2,501,497 3/1950 Clark et a1. 2,571,468 10/1951 Miller.

FOREIGN PATENTS 751,489 6/ 1956 Great Britain.

ROBERT K. SCHAEFER, Primary Examiner.

D. SMITH, Assistant Examiner. 

1. A SNAP ACTION SWITCCH COMPRISING A RELATIVELY FLEXIBLE RESILIENT BLADE HAVING A LENGTH SUBSTANTIALLY GREATER THAN ITS BREADTH, SAID BLADE BEING GENERALLY FLAT IN ITS MAJOR PLANE AND HAVING A FORM ADJACENT ONE END TO OFFSET SAID ONE END FROM SAID MAJOR PLANE; A MOUNTING REGION FOR SAID FLEXIBLE BLADE INTERMEDIATE SAID FORM AND THE END OPPOSITE SAID ONE END; A RIGID BLADE FORMING A FRAME FOR AN OPENINGG IN ITS MAJOR PLANE, THE OPENING HAVING A WIDTH EXCEEDING THE WIDTH OF SAID FLEXIBLE BLADE; MEANS TO SECURE THE ENDS OF SAID FLEXIBLE BLADE TO SAID RIGID BLADE SUCH THAT THE PORTION OF SAID FLEXIBLE BLADE ADJACENT SAID FORM STANDS AWAY FROM SAID RIGID BLADE, SAID FLEXIBLE BLADE BEING IN LONGITUDINAL COMPRESSION AND SAID RIGID BLADE BEING IN TENSION, SAID FLEXIBLE BLADE IN A REGION INTERMEDIATE ITS ENDS BEING FREE TO MOVE WITHIN THE OPENING DEFINED BY SAID RIGID BLADE IN A DIRECTION NORMAL TO THE MAJOR PLANE OF SAID RIGID BLADE; A FIRST ELECTRICAL CONTACT RIGIDLY SECURED TO SAID RIGID BLADE AT ITS END REMOTE FROM SAID FORM ON SAID ADJACENT FLEXIBLE BLADE; A SUPPORT STRUCTURE; A MOUNTING MEANS SECURED TO SAID SUPPORT STRUCTURE AND TO SAID MOUNTING REGION FOR SAID FLEXIBLE BLADE TO SUPPORT SAID FLEXIBLE BLADE, SAID RIGID BLADE AND SAID FIRST CONTACT FOR MOVEMENT RELATIVE TO SAID SUPPORT STRUCTURE; A SECOND ELECTRICAL CONTACT ARRANGED TO COOPERATE WITH AND BE ENGAGED BY SAID FIRST CONTACT AND SUPPORTED BY SAID SUPPORT STRUCTURE; AND AN ACTUATING MEANS ENGAGED WITH SAID RIGID BLADE AND MOVABLE GENERALLY NORMAL TO THE MAJOR PLANE OF SAID RIGID BLADE ADJACENT ITS END ADJACENT SAID FORM ON SAID FLEXIBLE BLADE TO CARRY THE LINE OF SAID TENSILE FORCE BETWEEN THE ENDS OF SAID RIGID BLADE ACROSS THE LINES OF COMPRESSIVE FORCE BETWEEN THE ENDS OF SAID FLEXIBLE BLADE AND SAID MOUNTING REGION WHEREBY THE FIRST CONTACT IS SHIFTED IN ITS ANGULAR RELATION TO THE SECOND CONTACT WITH A FORCE IN ITS ANGULAR RELATION TO THE SECOND CONTACT WITH A FORCE OF SAID ACTUATING MEANS AND A FORCE OF SAID RESILIENCE OF SAID FLEXIBLE BLADE IN THE REGION OF SAID FORM, SAID FORCES ACTING ON THE LEVER ARM OF SAID RIGID BLADE. 